The Gordon Research Conferences are designed to promote in depth communication among the most active research workers in rapidly developing the important disciplines. These Conferences operate on a workshop format but also provide a forum for and stimulation to young new investigators. The 1977 Conference on Hormone Action is the sixth in this series which began in 1969 because of the rapid advances made simultaneously on three fronts: the role of receptors (both membrane-bound and nuclear localized), of adenylate cyclase and related enzymes, and of gene activation. Moreover, the relevance of these mechanisms to human disease, including hypertension, diabetes, cancer, growth and development problems, infertility and anti-fertility, has become increasingly apparent. This Conference will emphasize the following topics: The structure and dynamics of the plasma membrane; positive and negative regulation of membrane receptors for peptide hormones and catecholamines; heterogeneity and dynamics of steroid and peptide receptors; hormonal regulation of morphogenesis and development; membrane antibody probes; molecular biology of hormone action; new regulators of membrane-bound cyclases; somatic cell genetics in hormone action; hormones and cancer.